1. Field of the Invention
The present invention relates to a projection display apparatus in which a projection lens barrel is capable of being interchanged.
2. Description of the Background Art
The projection display apparatus configured so that the lens barrel is selected and interchanged according to the size of the screen or the distance to the screen is being widely used. In such a projection display apparatus, a so-called bayonet type is sometimes adopted for the attachment part with respect to the projection lens barrel in terms of facilitating the removal and ensuring the reliability of attachment.
The bayonet type is configured so that a bayonet flange arranged on the projection lens barrel side is sandwiched between the nail part of a mount ring to be screw coupled to the side of the projection display apparatus and the mounting surface, and the mount ring is rotated about the screw coupling part to be tightened to the mounting surface side thereby fixing the bayonet flange between the nail of the mount ring and the mounting surface (see e.g., Japanese Patent Application Laid-Open No. 2004-54040 (see abstract etc).
However, in the bayonet type, the worker tends to tighten the mount ring in excess to ensure attachment, thereby breaking the screw thread of the screw coupling part of the mount ring and the projection display apparatus.
In particular, the weight of the projection lens barrel used in the projection display apparatus is heavy since a lens of large aperture must be used to increase the lighting of the projecting image, and thus the worker is further motivated to tighten the mount ring more strongly.
In Japanese Patent Application Laid-Open No. 2004-54040 (see abstract etc), a configuration of preventing the mount ring from loosening is disclosed, but the prevention of the turning of the mount ring and the release thereof is performed by removing the lens hood, and thus the work becomes troublesome since the lens hood must be removed each time the projection lens barrel is to be removed.